Air supply fan device

ABSTRACT

An air supply fan device including: a fan casing disposed continuously to a combustion chamber containing a gas burner therein; an air supply fan contained inside of the fan casing, for supplying burning air to the gas burner; and a motor disposed outside of the fan casing, for rotating the air supply fan. The air supply fan device comprising: a ventilation hole formed by opening a fan casing constituting wall around a motor rotary shaft of the motor connected to the air supply fan; and a diaphragm valve body which is fixed to the ventilation hole and has a through hole, through which the motor rotary shaft is inserted, opened at the center thereof. The valve body being formed into a shape such that a gap is defined between the through hole and the motor rotary shaft when the inner pressure inside of the fan casing is negative during the rotation of the air supply fan while the gap is closed in tight contact of the peripheral edge of the through hole with the motor rotary shaft when the inner pressure inside of the combustion chamber or the fan casing is positive.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an air supply fan device in acombustion apparatus and, more particularly, to an air supply fan devicein which air-tightness is enhanced such that combustion exhaust gasstaying inside of a combustion chamber cannot leak from the air supplyfan device.

2. Description of the Related Art

A combustion apparatus for a water heater may be provided with an airsupply fan device including an air supply fan in a combustion chambercontaining a gas burner therein. In such an air supply fan device, whenthe temperature of air to be supplied into the combustion chamber isincreased, the temperature of a motor for rotating the air supply fandevice or a motor rotary shaft also is increased, thereby often raisinga fear of a trouble with the rotation of the motor. In, for example, acombustion apparatus of an FF type (forced draft balanced flue type)duplex supply/exhaust system in which a supply channel, through whichoutside air is supplied into a combustion chamber, and an exhaustchannel, through which combustion exhaust gas staying in the combustionchamber is exhausted to the outside, are constituted of a singlesupply/exhaust cylinder, the outside air to be supplied is heated by thecombustion exhaust gas, and therefore, the temperature of the motorrotary shaft is liable to be increased.

In view of the above, there has been conventionally proposed an airsupply fan device which takes measures against such an increase intemperature of a motor rotary shaft. Referring to FIGS. 6 and 7, a motorcooling ventilation hole 49 is formed in a fan casing constituting wall411 around a motor rotary shaft 43 connected to an air supply fan device41 inside of a fan casing 410, and further, a self-cooled fan 44, whichprojects by resiliency of a spring 47 during stoppage of rotation of amotor 42 so as to close the ventilation hole 49 (FIG. 6) whereasretreats against the resiliency of the spring 47 during the rotation ofthe motor 42 so as to open the ventilation hole 49 (FIG. 7), is disposedin the motor rotary shaft 43 outside of the fan casing 410 in an airsupply fan device (the related art) disclosed in Japanese PatentLaid-open No. H05-52321. In FIGS. 6 and 7, reference numeral 45designates a stopper, and further, 44 b denotes a base for theself-cooled fan 44.

With this configuration, when the self-cooled fan 44 is rotatedaccording to the rotation of the motor 42, an air passage is definedfrom the ventilation hole 49 to the fan casing 410 (FIG. 7), so that themotor rotary shaft 43 or the motor 42 is cooled. In contrast, when therotation of the motor 42 is stopped, the ventilation hole 49 is closedwith the base 44 b of the self-cooled fan 44 (FIG. 6), so thatcombustion exhaust gas staying inside of a combustion chamber can beprevented from flowing out (back) through the ventilation hole 49, thussuppressing a leakage quantity of the combustion exhaust gas from thecombustion chamber.

However, in the related art, the outer peripheral surface of the motorrotary shaft 43 and the inner circumferential edge of the ventilationhole 49 are not fully closed since there is a clearance k therebetweenwhen the motor 42 is stopped from being rotated (see FIG. 6). Inaddition, although the self-cooled fan 44 is urged by the spring 47, ifan inner pressure inside of the combustion chamber is increased, theself-cooled fan 44 may retreat outward of the fan casing 410 (i.e.,toward the motor 42) against the resiliency of the spring 47. As aconsequence, when the inner pressure inside of the combustion chamber orthe fan casing 410 becomes positive by, for example, outside air blowninto a supply/exhaust cylinder due to a blast, the clearance at theventilation hole 49 is enlarged, so that the combustion exhaust gasremaining inside of the combustion chamber flows back, to flow outthrough the ventilation hole 49. In this manner, with the conventionalstructure, it is difficult to suppress the leakage of the combustionexhaust gas from the combustion chamber against the positive pressureapplied to the combustion chamber and the fan casing.

SUMMARY OF THE INVENTION

The present invention has been accomplished to solve the above-describedproblems experienced in the related art. Therefore, an object of thepresent invention is to provide an air supply fan device, in which amotor rotary shaft or a motor can be securely cooled, and further,combustion exhaust gas can be prevented from leaking through aventilation hole at the time of application of a positive pressure to acombustion chamber or a fan casing.

According to the present invention, there is provided An air supply fandevice including: a fan casing disposed continuously to a combustionchamber containing a gas burner therein; an air supply fan containedinside of the fan casing, for supplying burning air to the as burner;and a motor disposed outside of the fan casing, for rotating the airsupply fan, the air supply fan device comprising:

a ventilation hole formed by opening a fan casing constituting wallaround a motor rotary shaft of the motor connected to the air supplyfan; and

a diaphragm valve body which is fixed to the ventilation hole and has athrough hole, through which the motor rotary shaft is inserted, openedat the center thereof;

the valve body being formed into a shape such that a gap is definedbetween the through hole and the motor rotary shaft when the innerpressure inside of the fan casing is negative during the rotation of theair supply fan while the gap is closed in tight contact of theperipheral edge of the through hole with the motor rotary shaft when theinner pressure inside of the combustion chamber or the fan casing ispositive.

With the above-described configuration, when the air supply fan isrotated and the pressure inside of the fan casing becomes negative, thevalve body is deformed in such a manner as to be sucked inside of thefan casing, thereby defining the clearance between the through hole andthe motor rotary shaft. And then, air flow is formed to flow into thefan casing through the through hole, thus cooling the motor rotary shaftor the motor.

In contrast, when the pressure inside of the combustion chamber or thefan casing becomes positive during the stoppage of the rotation of theair supply fan, the valve body is deformed in such a manner as to bepushed outward of the fan casing, so that the peripheral edge of thethrough hole is brought into tight contact with the motor rotary shaft,thus closing the clearance defined between the through hole and themotor rotary shaft. Thus, it is possible to prevent combustion exhaustgas staying inside of the combustion chamber from flowing, back outwardthrough the ventilation hole, and further, to prevent the combustionexhaust gas staying inside of the combustion chamber from leaking.

Preferably, the valve body is made of a rubber sheet, and further, isformed into a projecting or recessed shape in such a manner as toenlarge a pressure receiving area of a pressure receiving portion whichreceives an air pressure inside of the fan casing.

In this way, a pressure receiving portion is sensitive to a change inair pressure inside of the fan casing, so that the valve body is quicklydeformed. As a consequence, when the pressure inside of the fan casingbecomes negative, the clearance is quickly defined, and therefore, themotor rotary shaft can be quickly cooled. In contrast, when the pressureinside of the fan casing becomes positive, the clearance is quicklyclosed, and therefore, the combustion exhaust gas hardly leaks.

Additionally, the valve body is excellent in tightness of the peripheraledge of the through hole with respect to the motor rotary shaft owing tothe property of a rubber sheet, thereby exhibiting high sealability, soas to more securely prevent the combustion exhaust gas from leakingthrough the ventilation hole.

Preferably, the inner diameter of the through hole is greater than theouter diameter of the motor rotary shaft, so as to define a clearancetherebetween in the valve body when the inside and outside pressures ofthe fan casing are equal to each other.

Therefore, the motor rotary shaft cannot be brought into contact withthe through hole of the valve body when the motor is started to berotated. As a consequence, the valve body cannot be broken due to therotation of the motor, or an extra load cannot be exerted on therotation of the motor. Furthermore, the sealability of the valve bodycan be held for a long period of time when the pressure of thecombustion chamber is positive.

As described above, in the air supply fan device according to thepresent invention, the motor rotary shaft or the motor can be securelycooled, and further, the combustion exhaust gas can be securelyprevented from leaking through the ventilation hole when the positivepressure is applied to the combustion chamber or the fan casing.

Other objects, features and advantages of the present invention willbecome more fully understood from the detailed description givenhereinbelow and the accompanying drawings which are given by way ofillustration only, and thus are not to be considered as limiting thepresent invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view schematically showing the configuration of a waterheater, to which an air supply fan device in a preferred embodiment isapplied;

FIG. 2 is a cross-sectional view showing the entire configuration of theair supply fan device in the preferred embodiment;

FIG. 3 is a perspective view showing a valve body to be fixed to the airsupply fan device;

FIG. 4 is a cross-sectional view showing the valve body when a pressureinside of a fan casing becomes negative when an air supply fan isrotated in the air supply fan device;

FIG. 5 is a cross-sectional view showing the valve body when thepressure inside of the fan casing becomes positive when the rotation ofthe air supply fan is stopped in the air supply fan device;

FIG. 6 is a cross-sectional view showing a conventional air supply fandevice when rotation of a motor is stopped; and

FIG. 7 is a cross-sectional view showing the conventional air supply fandevice when the motor is rotated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A detailed description will be given below of a preferred embodimentaccording to the present invention with reference to the attacheddrawings.

FIG. 1 is a view showing the entire configuration of a combustionapparatus (i.e., a water heater), to which an air supply fan device in apreferred embodiment according to the present invention is applied; FIG.2 is a cross-sectional view showing the entire configuration of the airsupply fan device; and FIG. 3 is a perspective view showing a valve bodyto be fixed to the air supply fan device.

A water heater 1 serving as a combustion apparatus illustrated in FIG. 1is designed for an FF type (forced draft balanced flue type) duplexsupply/exhaust system including a supply/exhaust manifold 11 providedwith a duplex pipe. Inside of an apparatus body 10 of the water heater1, there is provided a combustion chamber 14 containing a gas burner 15and a heat exchanger 16 therein. An air supply fan device 2 iscontinuously disposed under the combustion chamber 14. Thesupply/exhaust manifold 11 is constituted of an inner pipe in a duplexpipe, that is, an exhaust cylinder 12 for allowing combustion exhaustgas to be exhausted from the combustion chamber 14 and an outer pipe,that is, a supply pipe 13 for taking air from the outside. The open endof the supply/exhaust manifold 11 is opened to the outside through awall of a room, at which the water heater 1 is installed. The exhaustpipe 12 is connected to the upper portion of the combustion chamber 14,and constitutes an exhaust channel for exhausting the combustion exhaustgas from the combustion chamber 14 to the outside. The supply pipe 13extends downward inside of the apparatus body 10, and the distal endthereof is continuously disposed in the air supply fan device 2 in anair-tight manner, thus constituting a supply channel for supplyingoutside air into the combustion chamber 14. Here, the combustion chamber14 and the supply/exhaust manifold 11 are connected to each other in anair-tight manner.

As shown in FIG. 2, the air supply fan device 2 includes: a fan casing20 continuously disposed in the combustion chamber 14 in an air-tightmanner; an air supply fan 21, or a sirocco fan housed inside of the fancasing 20, for supplying burning air to the gas burner 15; and a motor22 disposed outside of the fan casing 20, for rotating the air supplyfan 21. Onto one constituting wall 24 a sideways of the fan casing 20 isdisposed the air supply cylinder 13 in an air-tight manner, and further,a fixing plate 25 for the motor 22 is securely attached to the outersurface of a constituting wall 24 b opposite to the constituting wall 24a. The motor 22 is fixed to the fixing plate 25. A circular ventilationhole 26 is formed on the constituting wall 24 b of the fan casing 20,onto which the motor 22 is fixed. A motor rotary shaft 23 for the motor22 penetrates through the ventilation hole 26, and is connected to theair supply fan 21 housed inside of the fan casing 20. The inner diameterof the ventilation hole 26 is greater than the outer diameter of themotor rotary shaft 23. Therefore, an annular opening 27 is definedaround the motor rotary shaft 23. A circular diaphragm valve body 3 isdisposed around and in the ventilation hole 26.

As shown in FIG. 3, the valve body 3 is made of a circular rubber sheethaving an outer diameter greater than that of the ventilation hole 26,and includes a through hole 31 opened at the center in such a manner asto allow the motor rotary shaft 23 to be inserted therethrough and aflange 32 extending outwards in such a manner as to be fixed onto theconstituting wall 24 b of the fan casing 20. Incidentally, although theflange 32 is air-tightly attached to the inner surface of theconstituting wall 24 b of the fan casing 20 in the valve body 3 shown inFIG. 2, it may be air-tightly attached to the outer surface of theconstituting wall 24 b.

Referring to FIG. 2, a peripheral edge 31 a of the through hole 31 ofthe valve body 3 is formed in such a manner as to protrude toward theair supply fan 21 in a cylindrical shape. The inner diameter of thethrough hole 31 is slightly greater than the outer diameter of the motorrotary shaft 23, and therefore, a clearance 35 is defined therebetween.Therefore, the motor rotary shaft 23 cannot be brought into contact withthe through hole 31 at the time of start of rotation of the motor 22(pressure is equal inside and outside of the fan casing 20, see FIG. 2).Thus, it is possible to prevent the motor rotary shaft 23 from slidingin contact with the through hole 31 of the valve body 3 at the time ofthe start of the rotation of the motor 22.

A region from the through hole 31 to the flange 32 in the valve body 3serves as a pressure receiving portion 33 for receiving an air pressureinside of the fan casing 20. The pressure receiving portion 33 isexpanded (projects) inward of the fan casing 20. In this manner, agreater pressure receiving area receiving the air pressure inside of thefan casing 20 can be provided, so that the valve body 3 can be quicklymoved according to a change in air pressure inside of the fan casing 20.Here, the pressure receiving portion 33 may be expanded (recessed)outward of the fan casing 20.

With the air supply fan device 2 having the above-describedconfiguration, the gas burner 15 in the combustion chamber 14 burns theair, and then, the air supply fan 21 is rotated, so that the outside airis supplied as the burning air from the air supply cylinder 13 into thecombustion chamber 14 through the fan casing 20, thereby making theinner pressure of the fan casing 20 negative. Thereafter, as shown inFIG. 4, the valve body 3 disposed in the ventilation hole 26 is deformedin such a manner as to be sucked inward of the fan casing 20, so thatthe diameter of the through hole 31 of the valve body 3 is increased.Thus, a gap 34 is defined between the through hole 31 of the valve body3 and the motor rotary shaft 23. And then, the air around the motorrotary shaft 23 is sucked into the fan casing 20 through the ventilationhole 26 and the through hole 31 of the valve body 3. In this manner, theair around the motor 22 outside of the fan casing 20 flows between themotor 22 and the fan casing 20, as indicated by an arrow A in FIG. 4.That is to say, air flow A is formed to be sucked into the fan casing 20through the ventilation hole 26 and the through hole 31 of the valvebody 3. Thus, the air flow A can effectively cool the motor rotary shaft23 and the motor 22.

In contrast, if the inner pressure inside of the combustion chamber 14or fan casing 20 becomes positive by, for example, the outside air suchas a blast blowing into the supply/exhaust manifold 11 during thestoppage of the rotation of the air supply fan 21, the valve body 3 isdeformed in such a manner as to be pushed outside of the fan casing 20by air flow B from the inside of the fan casing 20 toward theventilation hole 26, as shown in FIG. 5. And then, the diameter of theperipheral edge 31 a of the through hole 31 projecting toward the airsupply fan 21 in a cylindrical shape in the valve body 3 is reduced, thegap 34 between the through hole 31 and the motor rotary shaft 23 isclosed in tight contact with the motor rotary shaft 23. As aconsequence, even if the combustion exhaust gas staying inside of thecombustion chamber 14 reversely flows into the fan casing 20, thecombustion exhaust gas can be prevented from flowing outward through theventilation hole 26, thus securely preventing the combustion exhaust gasstaying inside of the combustion chamber 14 from leaking from the airsupply fan device 2. In addition, the valve body 3 can exhibit a highsealability owing to excellent air-tightness of the peripheral edge 31 aof the through hole 31 with respect to the motor rotary shaft 23 due tothe properties of the rubber sheet, thus further securely preventing thecombustion exhaust gas from leaking through the ventilation hole 26. Theoutside pressure of the air supply fan device 2 becomes negative byventilating the room, at which the water heater 1 is installed, so thateven if the air pressure inside of the combustion chamber 14 or the fancasing 20 becomes high (substantially, the pressure inside of thecombustion chamber 14 or the fan casing 20 is positive), the valve body3 is deformed to close the gap 34 defined between the through hole 31and the motor rotary shaft 23, as shown in FIG. 5.

As described above, with the air supply fan device 2 in the presentembodiment, the motor rotary shaft 23 or the motor 22 can be effectivelycooled when the air supply fan 21 is rotated. During the stoppage of therotation of the air supply fan 21, the combustion exhaust gas remaininginside of the combustion chamber 14 can be securely prevented fromleaking through the ventilation hole 26 of the fan casing 20 even if thepositive pressure is applied inside of the combustion chamber 14 or thefan casing 20.

When the inside and outside pressures of the fan casing 20 are equal toeach other, the inner diameter of the through hole 31 of the valve body3 is greater than the outer diameter of the motor rotary shaft 23, thusdefining the clearance 35. As a consequence, when the motor 22 isstarted to be rotated, the motor rotary shaft 23 cannot be brought intocontact with the through hole 31 of the valve body 3. Thus, it ispossible to prevent the valve body 3 from being damaged by the rotationof the motor 22 or an extra load from being exerted on the rotation ofthe motor 22, and further, to maintain the sealability of the valve body3 for a long period of time when the inside pressure of the combustionchamber 14 is positive.

The valve body 3 is made of the rubber sheet, and further, the pressurereceiving portion 33 is formed into a projecting or recessed shape so asto enlarge the pressure receiving area, at which the air pressure insideof the fan casing 20 is received. Consequently, the valve body 3sensitively reacts against the change in air pressure inside of the fancasing 20, to be deformed quickly. Therefore, when the inner pressureinside of the fan casing 20 becomes negative, the gap 34 is quicklydefined, thereby quickly cooling the motor rotary shaft 23 or the like.In contrast, when the inner pressure inside of the fan casing 20 becomespositive, the gap 34 is quickly closed, thereby virtually preventing anyleakage of the combustion exhaust gas.

Additionally, unlike the related art shown in FIGS. 6 and 7 in which theself-cooled fan is provided in the motor rotary shaft 23, the air supplyfan device 2 produces the following advantages. That is, the motor 22can be fixed near the fan casing 20, thus configuring the compact airsupply fan device 2; there is no problem of occurrence of noise inassociation with the rotation of the self-cooled fan; no extra load forrotating the self-cooled fan is exerted on the motor 22; and cost neednot be increased since no self-cooled fan is provided.

The present invention is not limited to the above-described embodiment,but various modifications can be embodied within the scope of thepresent invention.

For example, the outline shape of the valve body 3 or the shape of theventilation hole 26 is not limited to a circle, but may be a polygonsuch as a square.

In addition, the air supply fan device 2 according to the presentinvention is not limited to the water heater, but may be applied to acombustion apparatus for a heater or appliances other than thecombustion apparatus of the FF type (forced draft balanced flue type)duplex supply/exhaust system.

The present application claims a priority based on a Japanese PatentApplication No. 2008-304785 filed on Nov. 28, 2008, the content of whichis hereby incorporated by reference in its entirely.

1. An air supply fan device including: a fan casing disposedcontinuously to a combustion chamber containing a gas burner therein; anair supply fan contained inside of the fan casing, for supplying burningair to the gas burner; and a motor disposed outside of the fan casing,for rotating the air supply fan, the air supply fan device comprising: aventilation hole formed by opening a fan casing constituting wall arounda motor rotary shaft of the motor connected to the air supply fan; and adiaphragm valve body which is fixed to the ventilation hole and has athrough hole, through which the motor rotary shaft is inserted, openedat the center thereof; the valve body being formed into a shape suchthat a gap is defined between the through hole and the motor rotaryshaft when the inner pressure inside of the fan casing is negativeduring the rotation of the air supply fan while the gap is closed intight contact of the peripheral edge of the through hole with the motorrotary shaft when the inner pressure inside of the combustion chamber orthe fan casing is positive.
 2. The air supply fan device according toclaim 1, wherein the valve body is made of a rubber sheet, and further,is formed into a projecting or recessed shape in such a manner as toenlarge a pressure receiving area of a pressure receiving portion whichreceives an air pressure inside of the fan casing.
 3. The air supply fandevice according to claim 1, wherein the inner diameter of the throughhole is greater than the outer diameter of the motor rotary shaft, so asto define a clearance therebetween in the valve body when the inside andoutside pressures of the fan casing are equal to each other.